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    <title>Document</title>
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<body>
    <script>
        var arr = [[], [], [], [], []];

        for (var i = 0; i < arr.length; i++) {
            var brr = arr[i];
            console.log(brr);
            // 第一次brr(i=0) 1+5*0  2+5*0  3+5*0  4 5
            for (var j = 1; j <= 5; j++) {
                var num = j + 5 * i;//1 2 3 4 5 
                brr.push(num)
            }

            // 第二次brr  1 +5*1   2+5*1 3+5*1
            // 第三次brr  1 +5*2   2+5*2 3+5*2
        }

        console.log(arr);


        for (var i = 0; i < arr.length; i++) {
            // 通过i 获取一维数组的元素 brr

            var brr = arr[i];
            for (var j = 0; j < i + 1; j++) {
                // 00
                // 10 11 
                //  j 获取了 
                document.write(brr[j] + ' ')
            }
            document.write('<br>')
        }

    </script>

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